Hydromorphone: Physiological effects

Last modified: Sunday, 31. May 2009 - 4:21 pm

Hydromorphone and other narcotic analgesics have specific effects on the central nervous system in the body. These effects are produced through the binding of opioid-specific receptors in the brain. Hydromorphone also produces similar effects in organs in the body that contain smooth muscle. The primary therapeutic effects of hydromorphone are analgesia and sedation. One of the most important aspects of narcotic analgesics, such as hydromorphone, is that they produce significant analgesia without causing a loss of consciousness. Hydromorphone affects the respiratory center in the brain, and this is why it suppresses the cough reflex. Hydromorphone is partially broken down, or metabolized, by the liver and is absorbed by a variety of tissues and organs, including the gastrointestinal tract, smooth muscle, skeletal muscle, pancreas, lungs, cardiovascular system, and central nervous system. Once metabolized by the liver, hydromorphone moves out of the body by way of the kidneys and into the urine. The precise mechanisms by which hydromorphone and the other narcotic analgesics work are not entirely known. The levels of hydromorphone usually peak in the body about 45 minutes after oral administration of the drug. Injections into muscle produce effects within 15 to 30 minutes and reach peak levels between one-half to one and one-half hours later. The duration of effect usually lasts four to five hours. The actual amount of hydromorphone prescribed or administered depends on a variety of factors, including age, the degree of pain, the amount of opioid tolerance, and the body mass of the patient. Hydromorphone produces pain-relieving qualities in the central nervous system. It also tends to produce a euphoric feeling in the user. Negative effects by way of the central nervous system include decreased blood pressure and slowed breathing. Hydromorphone slows down the processes of the gastrointestinal tract and commonly causes constipation. Patients taking hydromorphone need to increase water and fiber intake to prevent and treat constipation. The most common side effects associated with the use of hydromorphone are increased sweating, light-headedness, dizziness, sedation, mental depression, nausea, and vomiting. Less commonly seen side effects include weakness, headache, muscle rigidity, decreased feeling in the extremities, double vision, hallucinations, disorientation, muscle coordination problems, muscle tremor, hearing loss, agitation, euphoric feelings, blurred vision, and insomnia. Additional side effects can include changes in heart rhythm, chills, decreased blood pressure, increased blood pressure, diarrhea, cramps, itching, dry mouth, skin flushing, breathing alterations, constipation, anorexia, cramps, alterations in taste, skin rashes, and urinary difficulties. Patients with a history of cardiovascular, respiratory, or intestinal problems should use hydromorphone with great caution. One of the most serious and overlooked side effects that develops from the long-term use of opioids is the potential for serious dehydration. Hydromorphone has comparable side effects to those produced by morphine use. This is true for sedation, respiratory depression, and constipation, but hydromorphone is associated with less vomiting than morphine. Nausea caused by hydromorphone and other opioids can be minimized by administering the drug along with food and having the patient lie down following administration. Extra caution should be taken when hydromorphone is prescribed to the elderly, those with significant physical impairment, and those with a history of liver, lung, or kidney disease. In addition, those with thyroid problems, Addison’s disease, central nervous system depression, coma, psychosis caused by toxic agents, and those with a history of gallbladder disease should receive hydromorphone only with great caution. The same is true for persons with a history of prostate enlargement, a narrowing of the urethra, severe alcoholism, delirium tremens, recent gastrointestinal surgery, or severe scoliosis.Harmful side effects Using more than the recommended dose of hydromorphone can cause a variety of serious health complications, such as convulsions, coma, and death. Early symptoms of overdose include confusion, nervousness, dizziness, low blood pressure, severe weakness, decreased pupil size, drowsiness, and slowed breathing. Later manifestations of serious overdose include significant changes in heart rate, low blood pressure, coma, and cardiac arrest. Persons who overdose on hydromorphone are usually treated with narcotic antagonists, such as naloxone. It is vital for the attending emergency physician to maintain respiratory function in these patients. Naloxone not only helps reduce the effects of hydromorphone throughout the body but also has specific respiratory-protecting effects. Individuals who have developed tolerance to opioids and who have overdosed on hydromorphone are not likely to develop the serious depression of the respiratory system that occurs in individuals with no such tolerance who have overdosed on hydromorphone. The typical treatment of narcotic overdoses with narcotic antagonists can lead to a severe withdrawal reaction in those who have developed tolerance to opioids. The Food and Health Administration has placed hydromorphone in the pregnancy category C. This means that pregnant women should receive hydromorphone only with great caution and should receive a high-potency formulation only when it is absolutely necessary. This classification is based on animal studies that suggest birth defects are more likely in animals receiving high doses of the drug. There have been no strictly controlled scientific studies in humans. Women who are breastfeeding should likewise use caution before taking hydromorphone. This caution is based on the fact that low levels of narcotic drugs have been found in the milk of mothers who use these drugs. Therefore, Mosby’s Medical Drug Reference recommends that nursing mothers not use hydromorphone. Women who are breastfeeding should inform their doctor or dentist that they are nursing if they require a strong prescription pain medication. Persons with a history of acute bronchial asthma should not receive hydromorphone. Persons with a history of head injury, increased pressure within the brain, seizures, serious abdominal problems, liver disease, kidney disease, thyroid disease, prostate disease, and low blood pressure should use hydromorphone with great caution. Also, the elderly should receive hydromorphone with great caution.Long-term health effects The primary long-term concern of those who use hydromorphone is the risk of addiction. The National Institute on Drug Abuse has determined that persons who become addicted to hydromorphone and other narcotic analgesics are at increased risk of convulsion, overdose, and death. Persons with a history of drug abuse of any kind should not receive hydromorphone unless absolutely necessary because of the great potential for addiction. Hydromorphone can become addictive for anyone who has received doses higher than those prescribed by a doctor and in those who use the drug for recreational purposes. In addition, those who receive the drug at prescribed levels for a lengthy period are at a relatively slight increased risk of addiction.